Rotary compressors are classified as positive displacement compressors which confine successive volumes of fluid within a closed space in which the pressure of the fluid is increased as the volume of the closed space is decreased.
A specific type of rotary compressor is known in the art as a sliding vane rotary compressor Sliding vane rotary compressors are of two different types. The first type is constructed to include a plurality of sliding vanes within the roller. Between each pair of sliding vanes is defined a closed space which is decreased in volume in order to compress the fluid therein.
Another type of sliding vane rotary compressor provides a single sliding vane which reciprocally engages the surface of the roller. A closed space is defined between the point at which the roller contacts the inside surface of the cylinder and the single sliding vane. Fluid is trapped between the roller and the sliding vane as the roller passes an inlet opening. Further rotation of the roller reduces the volume of the space in which the fluid is trapped. The pressure of the trapped fluid rises until reaching discharge pressure at which time the discharge valve opens and the fluid is expelled from the cylinder.
A typical sliding vane rotary compressor is shown in FIG. 1. The compressor includes a housing 10 having a fluid input 12 and a fluid output 14. A sliding vane 16 is reciprocally mounted within a cylinder housing 18. The cylinder housing 18 includes a cylindrical opening which has disposed therein a shaft 20 and a roller 22. The shaft 20 is hollow. The roller 22 is operably coupled to the shaft 20 though a cam 24. The roller 22 rotates upon the surface of the cam 24. The roller 22 remains in contact with the internal surfaces of the cylindrical opening in the cylinder 18 during its rotation due to its rotation on the surface of the cam 24. The ends of the roller 22 abut against top bearing plate 26 and the bottom bearing plate 28. The top bearing plate 26 closes the top end of the cylindrical opening and the bottom bearing plate 28 closes the bottom end of the cylindrical opening.
As described above, in the sliding vane rotary compressor shown in FIG. 1, fluid is compressed by decreasing the space between the roller 22 and the sliding vane 16 due to the rotation of the roller 22. The compressed fluid is expelled from the cylinder housing 18 into the housing 10. The bottom half 30 of the housing has contained therein oil for lubricating the compressor. Pressurized fluid and oil in the bottom half 30 of the housing 10 flows into a shaft opening 32 of the shaft 20. Due primarily to the rotation of the shaft 20, pressurized fluid and oil flows in an upward direction in the hollow shaft 20 and is output from oil holes 34, 36 and 38 of the shaft 20. Hole 40 in the shaft 20 is a breather hole. Oil flowing from each oil hole lubricates a moving part of the compressor.
Pressurized fluid and oil from oil holes 34, 36 and 38 flow into an internal space 41 within the roller 22. Pressurized fluid and oil eventually flows from the internal space 41 within the roller 22 through an opening in the top bearing plate 26 to lubricate a shaft bearing located in the top bearing plate 26. Pressurized fluid and oil from internal space 41 also flows down through an opening in the bottom bearing plate 28 to lubricate a shaft bearing located in the bottom bearing plate 28. After lubricating the shaft bearings the pressurized fluid and oil separates. The oil returns to the bottom half 30 of the housing 10 and the pressurized fluid travels up to the top half 42 of the compressor and cools the electric motor 43 which rotates the shaft 20.
Pressurized fluid from the top half 42 of the housing 10 is output by the fluid output 14. Being that pressurized fluid flows within the internal space 41 of the roller to the top half 42 of the compressor, a good seal between the ends of the roller 22 and the top and bottom bearing plates 26 and 28 is important. The efficiency of the sliding vane rotary compressor is primarily effected by the seal between the ends of the roller 22 and the top and bottom bearing plates 26 and 28. A good seal between the ends of the roller 22 and the top and bottom bearing plates 26 and 28 prevents the leakage of the pressurized fluid within the internal space 41 to the cylindrical opening in the cylinder housing 18 wherein fluid at a lower pressure is being compressed.
One important requirement with regard to rotary pumps is that the apparatus or method used to form a good seal between the ends of the roller and the bearing plate surfaces must be easily duplicated and lend itself to the interchange of defective parts so that maintenance and repairs can be easily accomplished.
Various methods and apparatus have been proposed for forming a good seal between the ends of the roller and the bearing plates.
For example, it has been proposed that the cylinder housing and the roller be machined to loose tolerances and later custom fitted to each other. This proposed method adds additional steps to the manufacturing and assembly process of a typical sliding vane rotary compressor which are time consuming and costly. Further, this proposed method suffers from the disadvantage of having cylinder housings and rollers which are custom fitted to each other thereby not permitting the interchange of the rollers and cylinder housings during repair and maintenance. Thus, this proposed method although providing a good seal between the ends of the roller and the bearing plates is not the most desirable solution where a large number of compressors are to be produced.
Another proposed method machines the cylinder housings and rollers to exact dimensions thereby improving the interchangeability of the cylinder housings and rollers. However, manufacturing a number of parts to such exact dimensions is extremely difficult, time consuming and costly.
Various other prior art devices have been proposed for forming a good seal between the ends of the roller and the bearing plates.
For example, U.S. Pat. Nos. 4,722,676 and 4,824,343 disclose spiral seals which fit snugly into grooves in the scroll of a scroll-type fluid transferring machine. The spiral shaped seals are designed to have various heights along its length in order to seal the scroll to its bearing surfaces. Such a sealing device does not address the problems associated with a sliding vane rotary compressor. Further, being that the spiral shaped seals are disposed at various heights along its length, uneven wear in the seal results. Still further, the groove formed in the scroll has an inside and outside wall which are necessary to control possible shifting of the spiral shaped seal along its complete length.
U.S. Pat. No. 4,293,290 describes a positive displacement rotary pump having standard "O" ring and rubber seals for engaging the bearing surfaces adjacent each rotor. The seals disclosed by U.S. Pat. No. 4,293,290 suffers from the following disadvantage. Each rotor having an "O" ring or rubber seals thereon must be accurately positioned relative to its bearing surfaces in order that the "O" ring or rubber seals properly engage the bearing surfaces for a good seal.
U.S. Pat. Nos. 1,839,638 and 2,311,162 disclose various apparatus associated with a rotary compressor and a rotary type internal combustion engine. However, neither patent discloses apparatus for effectively sealing a rotor to its bearing surfaces.